This invention relates to rotating anodes for x-ray tubes where provision is made for relief of thermal stresses. Such tubes are known from U.S. Pat. No. 3,836,803.
In rotating anode x-ray tubes, as is known, the surface of the anode which provides the focus path is locally strongly heated when said surface is impinged by electrons in the production of x-rays. Said surface is thus subject to thermal expansion and causes stresses which can lead to the breakage of the anode. As it is obvious from the aforementioned U.S. Pat. No. 3,836,803, a rotating anode with several radial cuts became known for relieving thermal stress. Thermal stresses are to become smaller due to the subdivision of the anode into smaller parts so as to facilitate an adjustment towards one another.
Another problem in such anodes is the removal of heat. The heat capacity, on one hand, and the radiating capability can both be increased, as is known from British Pat. No. 1,300,477, by attaching parts of graphite to surfaces of the anode lying outside of the focus path. For soldering-on of such parts of graphite it is, however, disadvantageous that the solder can penetrate the thermal stress relieving cuts of the known anode. The disadvantage from this can be realized particularly since the stress-release effect of the cuts is counteracted to a large extent by the penetration of solder. Moreover, solder cannot withstand the thermal load produced by the electron beam, because the melting point of solder compounds is considerably lower than that of the anode material.
The application of cuts, after the graphite parts are mounted, has been proven difficult. It depends on the form of the graphite, the solder and the cleaning of the finished plate. When applying the cuts, in particular to graphite, loose particles are produced at the edges of the cuts. Such loose particles are hard to remove and can interfere with the function of the x-ray tube, as do all loose particles in electron tubes, as is known.
Finally, the known embodiments with thermal stress relieving cuts have the additional grave disadvantage that their stability is lowered. This is of particular importance when the anode is rotated at a high revolution rate. The resulting centrifugal forces can cause the parts, separated by the cuts, to rupture.